The objective is to examine the mechanism by which sleep states alter respiratory patterning in the intact, freely moving cat. We suggest that state influences modify descending input from rostral brain regions to specific areas of the midbrain and medulla, and can be revealed by 1) examining "spontaneous" neuronal activity in particular regions of the ventral forebrain, midbrain, and medulla and relating this activity to respiratory patterning, and 2) evoking activity in rostral regions and examining the resultant influence on neuronal activity in respiratory brainstem regions and on respiratory activity. Microelectrodes and macroelectrodes will be placed in rostral regions that have a demonstrated effect on respiratory patterning in the waking state and subserve functions altered by different states, and thus may be a component of the respiratory stimulus of "wakefulness." Neuronal discharge and slow-wave activity will be recorded in rostral hypothalamic regions implicated in temperature control, hippocampal regions related t motor patterning, and the central nucleus of the amygdala, an area implicated in affective arousal. We will also record neurons in midbrain projection sites of these regions, the caudal lateral periaqueductal gray (which projects to premotor cells of facial, genioglossal, laryngeal, and abdominal motoneurons), the nucleus parabrachialis, and the Kolliker-Fuse nuclei of the parabrachial pons, as well as in the retroambiguus nucleus of the medulla. Respiratory pattern dependencies will be determined from cross-correlations of cell discharge with aspects of respiration as measured by patterning of the diaphragm, a laryngeal abductor (the cricothyroid), and two upper airway dilators (the posterior cricoarytenoid and genioglossus); linear regression procedures will be used to determine long-term relationships with aspects of the respiratory cycle and with blood pressure, measured with an indwelling carotid catheter. Phase=plane plots will be used to assess nonlinear aspects of respiratory patterning and neuronal discharge. Evoked activity will include warming and cooling of the preoptic region to manipulate temperature "drive" to respiration during each sleep-waking state, and excitation of affective responses with prey presentation and air mist. An efferent path from the hippocampus will be cold-blockaded to partially examine descending rostral influences to respiratory patterning.